Trastuzumab enhanced the cytotoxicity of Vγ9Vδ2 T cells against zoledronate-sensitized osteosarcoma cells

• Vγ9Vδ2 T cells can be expanded with ADCC (antibody-dependent cell-mediated cytotoxicity) potential.
• Vγ9Vδ2 T cells kill trastuzumab (TTZ)-coated osteosarcoma (OS) cell line U2OS through ADCC.
• In clinical relevant time, zoledronate (ZOL) stimulated only suboptimal cytotoxicity of Vγ9Vδ2 T cells.
• TTZ enhanced antitumor activity of Vγ9Vδ2 T cells to ZOL-sensitized OS cells.

Preliminary studies of Vγ9Vδ2 T cells and zoledronate (ZOL) present promising reasons to exploit their immunotherapeutic potential for osteosarcoma treatment (OS). ZOL is a third-generation aminobisphosphonate (ABP) and is well established in the management of cancer-induced bone disease. However, ZOL is characterized by high tropism for bone matrix, and the efficacy of ZOL for sensitizing tumors remains to be optimized. Vγ9Vδ2 T cells are important effectors of antibody-dependent cell-mediated cytotoxicity (ADCC). In this study, we investigated whether Vγ9Vδ2 T cell-mediated killing of ZOL-pretreated OS cells could be increased by the anti-HER-2 monoclonal antibody trastuzumab (TTZ). The cytotoxic activity of Vγ9Vδ2 T cells against osteosarcoma was assessed by an MTS assay in the presence or absence of TTZ. A CD107a assay was used to measure degranulation in cytotoxic Vγ9Vδ2 T cells. Blocking studies were used to determine the effect of relative ligands on Vγ9Vδ2 T cell recognition. TTZ induced an ADCC response in the OS cell line, U2OS; however, it had no effect on another OS cell line HOS with low levels of surface HER2 expression. Although the OS cells pretreated with ZOL for clinically relevant time periods (2 hours) stimulated a suboptimal immune response of Vγ9Vδ2 T cells, TTZ could further enhance the cytotoxicity of Vγ9Vδ2 T cells. These results demonstrate that combining TTZ and ZOL significantly increases the cytotoxic potential of Vγ9Vδ2 T cells. This study raises the possibility of utilizing ZOL and TTZ in Vγ9Vδ2 T cell-based immunotherapy for OS.